In a hybrid electric vehicle (HEV), an electric vehicle (EV), and the like, an assembled battery (battery system), which is constituted by connecting a plurality of battery cells of a second battery in series, has been typically used so as to secure a desired high voltage. In the related art, a battery managing device using an integrated circuit and the like is connected to the assembled battery for every predetermined number of battery cells for capacity calculation of each of the battery cells or protection management. A charged and discharged status of the battery cell is controlled by the battery managing device to perform management of the battery cell.
Particularly, in the case of an assembled battery using a lithium ion battery in a battery cell, the lithium ion battery has a high energy density. Accordingly, it is dangerous to enter an over-charged status due to an abnormal operation of the battery managing device. Therefore, to enhance reliability and stability of the battery managing device, a technology of PTL 1 is known. PTL 1 discloses a configuration in which pseudo-voltage information is input to a battery status detection circuit that detects a battery status of the battery cell to diagnose whether or not the battery status detection circuit normally operates.